Emission electrode for electrostatic precipitators



United States Patent O 3,200,566 EMISSION ELEQTlR-QDE FOR ELMZTRQSTATI CPRECTPITATURS Stig Gustafsson, Jonkoping, and Stein Maartmann, Klinten,Sweden, assignors to Alrtiebolaget venska Flakttabrn hen, Stockholm,Sweden Filed July 11, 1962, Ser. No. 209,182 Claims priority,application Sweden, daily 12, 1961, 7,224/61 3 Claims. (Cl. 55-152) Thepresent invention relates to an emission electrode for electrostaticprecipitators with a horizontal gas flow, each emission electrodeconsisting of a vertically mounted plate-like member made of sheet metalwith a fiat center part or web and bent-up or rolled vertical edgestiifening strips. Since the efiiciency of precipitation of anelectrostatic precipitator is highly depending upon the voltage used andas it can be proved that the efficiency in separation of heavier dust,that is to say with a particle size greater than 1 ,u, increases as thesquare of the voltage, it is of importance to make the electrostaticprecipitators in such a way that the voltage can be kept at the highestpossible value. With the types of emission electrodes used up to now thevoltage can, it is true, be kept high, but in such electrodes it hasbeen diflicult to provide a favorable current distribution without riskof flash-over. Especially in the cleaning of gases with high resistivedust this drawback has asserted itself. The invention, which relates toa new and improved embodiment of emission electrodes making possible ahigh voltage in combination with a favorable current distribution with alarger number of emitting projections per unit of surface, ischaracterized in that the edge strips are provided with a number ofpressed-up wart-shaped projections which constitute the main emittingelements of the electrodes.

The pressed-up wart-shaped projections are in accordance with thepresent invention, provided on the two edge strips of the electrode onopposite sides of the plane of the web of the electrode. Anotherembodiment is characterized in that the pressed-up wart-shapedprojections are directed towards opposite sides on each of the two edgestrips of the electrode. The wart-shaped projections can in both casesbe uniformly distributed along the edge strips, that is to say reckonedin the vertical extension of the electrode, or also be disposed in adifferentiated distribution.

The invention will now be described with reference to the accompanyingdrawing, which shows an electrostatic precipitator equipped withemission electrodes in accordance with the invention, and wherein:

FIG. 1 is a longitudinal vertical section through an electrostaticprecipitator;

FIG. 2 is an enlarged horizontal cross-section of one embodiment of anemission electrode having bent portions and wart-shaped projections onboth sides;

FIG. 3 is a view like FIG. 2 but showing an electrode having edge stripswith bent portions on only one side;

FIG. 2a is a partial side view of the FIG. 2 embodiment, taken on theline 2a-2a of FIG. 2; and

FIG. 3a is a partial side view of the FIG. 3 embodiment, taken on theline 3a3a of FIG. 3.

In the drawing 1 indicates the casing of an electrostatic precipitatorequipped with a number of vertical emission electrodes 2, arranged inparallel rows, which in a known way are swingably suspended in a frame3. The electrodes consist of sheet metal plate-like members with a fiatcenter part or web 3a with rolled or bent up edge stiffening 3,200,565Patented Aug. 17, 1965 "ice strips 3b and 30 respectively, as is moreevident from FIGS. 2 and 3 respectively. In accordance with theinvention the electrodes are provided with emitting elements in the formof pressed-up wart-shaped projections 4 along the edge strips. Thewart-shaped projections are, as shown in the drawing, roundedprojections connected to the curved bent portion of each stiifeningstrip and extending in a direction substantially perpendicular to theplane of each web. As illustrated in the drawing, each of the roundedprojections is pressed outwardly from the curved bent portion and has asubstantially hemispherical smooth and unbroken peripheral outline.These wart-shaped projections can, as shown in FIG. 2, at each of theedge strips be directed to both sides of the plane of the electrode web;or, at one edge strip, be directed to one side and at the other edgestrip to the opposite side as shown in FIG. 3. For the cleaning of theelectrodes there are arranged rapping rods 5 attached below theelectrodes and a rapping device 6 actuating said rods.

What we claim is:

1. An emission electrode for electrostatic precipitators in which anumber of vertical plate-like electrodes are arranged in a co-planar rowwith the planes of the plates disposed parallel to the flow of gasthereover transversely across the width and edges, said emissionelectrode comprising a continuous smooth planar web bent at eachlongitudinal edge to form a vertical stiffening strip having a curvedbent portion on at least one side of the plane of the web, and aplurality of vertically spaced, integral, rounded projections on thecurved bent portion of each stiffening strip, said projections extendingin a direction perpendicular to the plane of said web, each of saidprojections being pressed outwardly from said curved bent portions andhaving a substantially hemispherical smooth and unbroken peripheraloutline.

2. An emission electrode as set forth in claim 1, in which the bentportions at opposite edges of the web are directed in oppositedirections with respect to theplane of the web to place said roundedprojections in staggered relationship relative to the plane of the web.

.3. An emission electrode as set forth in claim 1, in which the verticalstifiening strip at each edge of the electrode has a bent portion withrounded projections on each side of the plane of the web.

References Cited by the Examiner UNITED STATES PATENTS 832,767 10/06Bridge 55--152 X 1,345,790 7/20 Lodge 55--129 X 1,767,338 6/30 Arras55-130 1,931,436 10/33 Deutsch 55--152 X $395,431 4/40 Shively et al55-152X 2,694,464 11/54 Winterrnute 55-152 2,737,258 3/56 Harlow 55154 X2,812,035 11/57 Sohlman et al 55112 2,946,400 7/ Gustafsson 55--1303,158,454 11/64 Gustafsson 55--154 X FOREIGN PATENTS 911,017 2/46France.

344,705 1 1/ 21 Germany.

888,871 2/ 62 Great Britain.

ROBERT F; BURNETT, Primary Examiner.

HARRY B. THORNTON, Examiner.

1. AN EMISSION ELECTRODE FOR ELECTROSTATIC PRECIPITATORS IN WHICH ANUMBER OF VERTICAL PLATE-LIKE ELECTRODES ARE ARRANGED IN A CO-PLANAR ROWWITH THE PLANES OF THE PLATES DISPOSED PARALLEL TO THE FLOW OF GASTHEREOVER TRANSVERSELY ACROSS THE WIDTH AND EDGES, SAID EMISSIONELECTRODE COMPRISING A CONTINUOUS SMOOTH PLANAR WEB BENT AT EACHLONGITUDINAL EDGE TO FORM A VERTICAL STIFFENING STRIP HAVING A CURVEDBENT PORTION ON AT LEAST ONE SIDE OF THE PLANE OF THE WEB, AND APLURALITY OF VERTICALLY SPACED, INTERGRAL, ROUNDED PROJECTIONS ON THECURVED BENT PORTION OF EACH STIFFENING STRIP, SAID PROJECTIONS EXTENDINGIN A DIRECTION PERPENDICULAR TO THE PLANE OF SAID WEB, EACH OF SAIDPROJECTIONS BEING PRESSED OUTWARDLY FROM SAID CURVED BENT PORTIONS ANDHAVING A SUBSTANTIALLY HEMISPHERICAL SMOOTH AND UNBROKEN PERIPHERALOUTLINE.